1. Field of the Invention
The present invention relates to a vehicle lamp unit employing a semiconductor light source, such as a light emitting diode-(LED) and an electroluminescent (EL or organic EL) device, and a vehicle headlamp using the vehicle lamp unit.
2. Description of the Related Art
There have been known vehicle lamp units of this type and vehicle headlamps using the vehicle lamp units. A conventional vehicle headlamp is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-317513. The conventional vehicle headlamp includes a reflective surface, a semiconductor light emitting element such as an LED as a light source, and a projection lens. When the semiconductor light emitting element is lit to emit light, the light emitted from the semiconductor light emitting element is reflected by the reflective surface. The light reflected by the reflective surface is emitted through a projection lens to the outside with a predetermined light distribution pattern and illuminates a road surface and the like.
Light emitting properties of an ordinary LED, for example, an ordinary Lambertian LED are explained below with reference to FIGS. 5 and 6. In FIGS. 5 and 6, reference letters H-H indicate a planar direction of a light emitting chip (light emitting portion 10) of an LED (semiconductor light source 6), and reference letters V-V indicate a vertical direction with respect to the planar direction H-H of the light emitting chip (light emitting portion 10) of the LED (semiconductor light source 6). The vertical direction V-V passes through an substantially center of the light emitting chip (light emitting portion 10) of the LED (semiconductor light source 6). As is clear from FIGS. 5 and 6, a relative intensity of the light emitted from the LED (semiconductor light source 6) is the maximum (100%) when angular displacement is 0 degree (vertical direction V-V). The relative intensity of the light emitted from the LED (semiconductor light source 6) gradually decreases as the angular displacement moves toward the planar direction H-H. For example, when the angular displacement is +70 degrees and −70 degrees, the relative intensity is about 20%. Furthermore, the relative intensity of the light emitted from the LED (semiconductor light source 6) is the minimum (0%) when the angular displacement is 100 degrees.
However, in the conventional vehicle headlamp, the planar direction of the light emitting chip of the LED being the semiconductor light emitting element is substantially parallel to an optical axis of the projection lens. In other words, the vertical direction (emission direction with the maximum light emission intensity) of the light emitting chip of the LED, being the semiconductor light emitting element, is substantially perpendicular to the optical axis. Therefore, in the conventional vehicle headlamp, most of lights emitted from the semiconductor light emitting element of which relative intensity is comparatively high are reflected downwardly with respect to the optical axis, by the reflective surface which is located above the semiconductor light emitting element. On the other hand, a small amount of lights, among the lights emitted from the semiconductor light emitting element, of which relative intensity is comparatively low, are reflected by the reflective surface in substantially parallel to the optical axis. As is clear from these, in the conventional vehicle headlamp, there is substantially no light, among the lights emitted through the projection lens, which is substantially parallel to the optical axis. Particularly, in the case of the vehicle headlamp which emits a light distribution pattern for oncoming traffic and a light distribution pattern for an expressway, both of which have cut-off lines, each light intensity (illumination, light amounts, etc.) along the cut-off lines of the light distribution patterns is low.